Case study of Najafgarh Drain - A rich wetland ecosystemin Delhi turning into a highly polluted water body Dr.Nibedita Khuntia*, Esha Govil**, Vikas** and Cessna Sahu** *Assistant Professor, Department of Biology, ** B. Tech, Department of Computer Science– Maharaja Agrasen College, Universityof Delhi Abstract Over the past years due to rigorous agricultural practice, urbanization,rapid industrialization and daily household activities, water pollution has becomea major issue. These factors have played havoc on a water body in the national capital of India as well.The famous Najafgarh Drain in Delhi, once a rich wetland,has turned into one of the most polluted water body in the country. This paper discusses the ecological importance of the drain, the causes and effects of the subsequent decline in its quality. It also discusses the findings of two field visits undertaken to understand the local effects of water pollution of the drain on the lives of residents who live in proximity of the drain. Keywords: Najafgarh Drain, pollution loads, industrialization, urbanization, sewage disposal, environmental degradation Introduction: The famous Najafgarh drain (See Map in Figure 1) in the national capital of the country got its name from a town called Najafgarh in South West Delhi. It is now recognized as the “Ganda Nallah” by the residents of the city due to high levels of pollution. The situation is so bad, that in 2005, the Central Pollution Control Board (CPCB) stamped it as a highly polluted drain and put it under “D” category with other 13 highly polluted wetlands(7). This wasn't always the state of the drain. The drain had ecological importance previously, which has now been undermined. Background of the Nallah The Najafgarh drain is in fact part of “Sahibi”, a rain-fed river originating in Rajasthan. This river makes its way through the state of Haryana and then finally enters Delhi near a village called Dhansa, where it spills its overflow. This spillover led to the formation of a lake, called the Najafgarh lake, which was seasonal in nature and could span an area of 300 square kilometers. The water continued to flow from the other side of the lake, through a narrow channel called the Najafgarh drain, which eventually joined the Yamuna river. The presence of this lake created a rich habitat for birds and other wildlife. During the winter months, the lake became home to several migratory birds. Before independence, the British ornithologist, Allan Octavian Hume, reported sighting birds like the Pink-headed Duck and Siberian Crane here. Due 94 | P a g e to these frequent sightings, it was even proposed to be a bird sanctuary and important wildlife habitat(3). In 1978, the drain was repurposed to drain flood and storm water from the city of Delhi. Such action was prompted because the previous year, water levels in the lake and the channel had increased, posing a threat of submersion to the households nearby. Fig:1 Najafgarh Drain of NCT Delhi (https://www.researchgate.net/figure/Delhi-map-with-inset- of-India-map-showing-Najafgarh-drain_fig2_257767339) Water pollution in Najafgarh Drain The Najafgarh drain is highly polluted and is recorded as the most polluted water body in the National Capital Region (NCR), mainly due to direct disposal of the untreated sewage into the water (1). The industries located along its course, directly dump the hazardous waste into this drain making it highly polluted and causing the lake ecosystem to become unsuitable for 95 | P a g e sustaining life. This drain also passes through the urbanized area. The people living nearby the surrounding areas, dump their daily garbage into the drain. This makes the drain smelly and difficult for the people living nearby to survive(12). Specifically, the severed catchment area of the drain is approximately 400 km. Due to severe constraints in the sewage system, the Najafgarh drain carries a large amount of raw sewage. Figure 2 shows the dirty water presently flowing through the drain. In addition, it receives treated effluent from various Sewage Treatment Plants (STP's) and freshwater from Western Yamuna Canal. Fig 2: Photo of Najafgarh drain at present (https://economictimes.indiatimes.com/news/politics- and-nation/central-pollution-control-board-report-shows-clean-yamuna-a-distant- dream/articleshow/53279581.cms?utm_source= content of interest & utm_medium = text &utm_campaign=cppst) The combined discharge is over 2100 Million Litre per Day (MLD) out of which about 600 MLD (30%) is treated which represents 50% of hydraulic load and over 25% of inorganic load from NCT Delhi into river Yamuna. The flow in Najafgarh drain is divided into three Stages. The Background Flow is about 150 MLD before the drain enters NCT Delhi. Almost 40% flow is untreated while the rest 60% is discharged after conventional treatment (13). This water has a Biological Oxygen Demand (BOD) of around 100 mg/L. Next is the flow that originates from Delhi. Due to limited sewerage systems, large quantities of untreated sewage from the secondary drains enter the Najafgarh drain. As per a study, 38 out of the identified 48 secondary drains carry significant flows (7). Water from all three sectors i.e. domestic, industrial and agriculture contribute into wastewater loads in the Najafgarh drain. The largest contributor is the domestic sector due to a large population living around the drain. Around 1340 MLD wastewater is discharged from the domestic units followed by 150 MLD from industries and a negligible contribution from agriculture. Approximately 78% of BOD is contributed by the domestic sector(10). All these sources and various anthropogenic activities are adding harmful substances, 96 | P a g e oxidized organics, inorganic, suspended solids, sewage and harmful pathogens into the Najafgarh drain. In the final stage, dilution of wastewater takes place due to the addition of 450MLD fresh water from the Western Yamuna Canal. Here BOD dilution of about 65% takes place just at the outfall into river Yamuna and is reported to be 125 mg/L (14). The pollution of Najafgarh drain has serious consequences for the river it joins, Yamuna. In 2012, it was observed that levels of biochemical oxygen demand (BOD) and Total Coliform measured at Nizamuddin Bridge, Kalindi Kunj, Okhla and Palwal monitoring stations in Delhi were much above the permissible limits (9). The BOD level at Nizamuddin Bridge was almost 12 times the permissible limit of 3 mg/litre prescribed by the Central Pollution Control Board. The total coliform was almost 3 million times higher. A report by the Central Pollution Control Board submitted to the National Green Tribunal (NGT) on the city’s sewage treatment shows why it is highly unrealistic to expect a clean Yamuna anytime soon. The report states that against a generation of 4,200 million liters a day (MLD) of wastewater, about 1,951.67 MLD is being treated while the rest is being discharged into the river directly. The only time there is fresh water in the river is during the monsoon, which effectively means that for the rest of the year, the river is itself a huge drain. It reveals that 31 out of the 40 sewage treatment plants in the city are unable to treat sewage according to the new norms with respect to various parameters like total suspended solids, biochemical oxygen demand and chemical oxygen demand (COD). Fig 3: Sewage Waste going into Najafgarh Drain (Picture taken by the Survey Team) Such pollution has various adverse effects. Due to the increase in the organic components in the water of Najafgarh drain, it became the habitat of various microorganisms, which released gases like Methane (CH4), Hydrogen Sulphide (H2S),Carbon Dioxide (CO2) etc. as byproducts of their physiological processes. It created a situation where the BOD increased substantially, compromising the survival of aquatic organisms. 97 | P a g e Recently, the Asian Waterbird Census (AWC) 2017 was carried out at Najafgarh Lake by a team of volunteers who were accompanied by AWC Delhi State coordinator and ecologist T. K. Roy. The Water bird census highlighted that 33 water bird species were seen, with a total population of 1,317(11). Of these, there were 13 resident and local migratory water-bird species, and 20 are winter migratory water birds, including four species who happen to be on the Red List of threatened birdsas declared by the International Union for Conservation of Nature (IUCN). It was confirmed that there are in fact fewer birds in the year this survey. There was a good monsoon in the year 2016 which had revived the Najafgarh lake, but it dried up again the winter season of 2016 which led to the shrinking of bird habitat. The AWC 2017 has recorded less water bird diversity and lower population in comparison with previous AWC results. (12) . The gases released also have several effects. These gases have a foul smell and corrode the electronic gadgets of residents nearby, posing a huge problem to them. The pollution in the drain has also caused several health-related issues, particularly breathing problems that further aggravate blood pressure, leading to cardiac arrests and other catastrophic effects. Not only that, the risk of vector borne diseases also increases due to the presence of contaminated water - which serves as breeding ground for mosquitoes and insects. Field Visit: Preliminary Findings In order to understand the local issues facing people and the environment due to the Najafgarh drain pollution, field visits to two residential areas were organized. One visit was to Dwarka, an area where harmful effects of the drain have been well recorded. The other visit was to Sagarpur, from which a tributary of the Najafgarh drain passes. The findings from the two visits are highlighted here.